[EXIM] Conditional route_list smarthost

Is it possible to construct a condition route_list for smarthost?

I tried the following:

smarthost:
  driver = domainlist
  transport = remote_smtp
  route_list = "* ${if match{$header_from:}{*.usa.net} \
                {<smarthost1>}{<smarthost2>} bydns_a"

But was hit by the following error:

smarthost router deferred: smarthost router: failed to expand "${if":
unknown condition ""
*** Frozen ***

Any help appreciated.

--
H Huang

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